linux-kernel - [PATCH] io-mapping: remove fallback for writecombine

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Date:   Wed, 20 Oct 2021 13:48:38 -0700
From:   Lucas De Marchi <lucas.demarchi@...el.com>
To:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Cc:     Chris Wilson <chris@...is-wilson.co.uk>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        linux-mm@...ck.org, Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] io-mapping: remove fallback for writecombine

The fallback was introduced in commit 80c33624e472 ("io-mapping: Fixup
for different names of writecombine") to fix the build on microblaze.

5 years later, it seems all archs now provide a pgprot_writecombine(),
so just remove the other possible fallbacks. For microblaze,
pgprot_writecombine() is available since commit 97ccedd793ac
("microblaze: Provide pgprot_device/writecombine macros for nommu").

This is build-tested on microblaze with the following hack to always
build mm/io-mapping.o and without diying on a x86-only macro
(_PAGE_CACHE_MASK)

Cc: Chris Wilson <chris@...is-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@...ll.ch>
Cc: Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>
Cc: linux-mm@...ck.org
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Lucas De Marchi <lucas.demarchi@...el.com>
---
 include/linux/io-mapping.h | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/include/linux/io-mapping.h b/include/linux/io-mapping.h
index e9743cfd8585..66a774d2710e 100644
--- a/include/linux/io-mapping.h
+++ b/include/linux/io-mapping.h
@@ -132,13 +132,7 @@ io_mapping_init_wc(struct io_mapping *iomap,
 
 	iomap->base = base;
 	iomap->size = size;
-#if defined(pgprot_noncached_wc) /* archs can't agree on a name ... */
-	iomap->prot = pgprot_noncached_wc(PAGE_KERNEL);
-#elif defined(pgprot_writecombine)
 	iomap->prot = pgprot_writecombine(PAGE_KERNEL);
-#else
-	iomap->prot = pgprot_noncached(PAGE_KERNEL);
-#endif
 
 	return iomap;
 }
-- 
2.33.1